Method for fabricating a liquid crystal display

ABSTRACT

A liquid crystal display includes a bottom substrate with a gate wire, a data wire and thin film transistors, and a top substrate with color filters. In a method for fabricating the liquid crystal display, a pixel electrode is formed on the bottom substrate at each pixel area using a first mask such that the pixel electrode has a first region with a smooth surface, and a second region with a rough surface. A common electrode is formed on the top substrate using a second mask such that the common electrode has a first region with a smooth surface, and a second region with a rough surface. The bottom substrate and the top substrate are assembled together, and a liquid crystal is injected between the bottom and the top substrates.

BACKGROUND OF THE INVENTION

[0001] (a) Field of the Invention

[0002] The present invention relates to a liquid crystal display andmore particularly, to a twisted nematic (TN) mode liquid crystaldisplay.

[0003] (b) Description of the Related Art

[0004] Generally, a liquid crystal display has a structure where aliquid crystal layer is sandwiched between two substrates; and anelectric field is applied to the liquid crystal to control lighttransmission. Of the two substrates, the bottom substrate is providedwith thin film transistors and pixel electrode, and the top substratewith a common electrode and color filters.

[0005] The twisted nematic (TN) mode has been mainly employed for use ina large size and high definition liquid crystal display because it hasthe advantages of structural stability and simplified processing steps.In the TN mode liquid crystal displays, the substrates are rubbed foralignment such that the directors of the liquid crystal molecules at thetop substrate are perpendicular to those of the liquid crystal moleculesat the bottom substrate.

[0006] In order to enhance the viewing angle, a multi-domain techniquehas been developed for the TN mode liquid crystal displays. In themulti-domain liquid crystal display, a number of differently-structuredliquid crystal domains are present at one pixel area. Assuming that agroup of liquid crystal molecules with the same direction of twisting isreferred to as the “domain,” the multi-domain liquid crystal displaybears multiple groups of liquid crystal molecules at one pixel area.

[0007]FIG. 1 illustrates a sectional structure of a two-domain twistednematic (TDTN) liquid crystal display at one pixel area according to aprior art.

[0008] As shown in FIG. 1, the liquid crystal panel 210 includes abottom substrate 201, a top substrate 202, and a liquid crystal layer209 sandwiched between the bottom and the top substrates 201 and 202. Afirst liquid crystal domain A where the liquid crystal molecules aretwisted in a first direction 1 is placed at the left side L of thepixel. A second liquid crystal domain B where the liquid crystalmolecules are twisted in a 10 second direction 2 is placed at the rightside R of the pixel.

[0009] The two liquid crystal domains A and B may be formed throughdifferentiating the pretilt angles of the liquid crystal molecules atthe bottom substrate 201 or the top substrate 202.

[0010] For instance the liquid crystal molecules placed at apredetermined region of the bottom substrate are established to have alarge pretilt angle, whereas those at the corresponding region of thetop substrate to have a small pretilt angle. Furthermore, the liquidcrystal molecules placed at another, region of the bottom substrate areestablished to have a small pretilt angle, whereas those at thecorresponding region of the top substrate to have a high pretilt angle.Even though the liquid crystal molecules placed close to the substratesare oriented depending upon the respective pretilt angles due to thecondition of the substrate, the liquid crystal molecules within theliquid crystal layer are oriented pursuant to the higher pretilt angle,resulting in two or more liquid crystal domains.

[0011] In the drawing, the respective liquid crystal domains A and Bbear different pretilt angles with respect to the bottom and the topsubstrates 201 and 202. For instance, the liquid crystal molecules atthe first liquid crystal domain A are tilted against the bottomsubstrate 201 at an angle of about 6-7°, while being tilted against thetop substrate 202 at an angle of about 0-1°. By contrast, the liquidcrystal molecules at the second liquid crystal domain B are tiltedagainst the bottom substrate 201 at an angle of about 0-1°, while beingtilted against the top substrate 202 at an angle of about 6-7°. Theinclined lines at the bottom and the top substrates 201 and 202 indicatethe pretilt angles of the liquid crystal molecules.

[0012] The pretilt angles of the liquid crystal molecules are determineddepending upon the surface roughness of alignment films (not shown). Thesurface roughness of the alignment film varies depending upon therubbing conditioning, the amount of light exposure, and the surfaceroughness of the ITO-based layer. Conventionally, the ITO-based pixelelectrode of the bottom substrate 201 and the ITO-based common electrodeof the top substrate 202 have various surface roughness, therebycontrolling the pretilt angles of the liquid crystal molecules close tothe respective substrates. When the surface roughness of the pixelelectrode is high, the pretilt angle of the liquid crystal molecules isreduced, whereas when the surface roughness of the pixel electrode islow, the pretilt angle of the liquid crystal molecules increases.Therefore, the pretilt angles of the liquid crystal molecules an becontrolled bases on the surface roughness of the pixel electrode.

[0013] In order to form such a pixel electrode, after the deposition ofthe pixel electrode layer, a photoresist pattern is formed on the pixelelectrode layer while exposing the portion to be surface-treated, andthe exposed portion of the pixel electrode layer is wet-etched using thephotoresist pattern as a mask.

[0014] However, in the above technique, a separate mask should beprovided to make surface treatment in addition to form the pixelelectrode layer. This complicates the processing steps and lowersproduction efficiency.

SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide a method forfabricating a multi-domain liquid crystal display bearing wide viewingangle characteristics without using an additional mask.

[0016] This and other objects may be achieved by a method forfabricating a liquid crystal display where a pixel electrode withdifferent surface roughness is formed at each pixel area using one mask.

[0017] According to one aspect of the present invention, in a method offabricating a liquid crystal display, a pixel electrode is formed, on abottom substrate at each pixel area using a first mask such that thepixel electrode has a first region with a smooth surface, and a secondregion with a rough surface, the bottom substrate having a gate wire, adata wire and a thin film transistor. And, a common electrode is formedon a top substrate using a second mask such that the common electrodehas a first region with a smooth surface, and a second region with arough surface, the top substrate having color filters; and the bottomsubstrate having the pixel electrode. And the top substrate is assembledwith the bottom substrate, and liquid crystal is injected between thebottom substrate and the top substrate.

[0018] In order to form the bottom substrate, a gate wire is formed on afirst insulating substrate. The gate wire includes gate line, and gateelectrode. A gate insulating layer is formed on the substrate such thatthe gate insulating, layer covers the gate wire. A semiconductor patternand a data wire are formed on the gate insulating layer. The data wireincludes data line, source electrode connected to the data line whilebeing connected to the semiconductor pattern, and drain electrode facingthe source electrode while being connected to the semiconductor pattern.A protective layer is formed on the substrate such that the protectivelayer covers the data wire. First contact holes are formed at theprotective layer such that the first contact holes expose the drainelectrode.

[0019] The first mask has a first region transmitting light with a firstlight transmissivity, and a second region transmitting the light with asecond light transmissivity lower than the first transmissivity. Thefirst and the second regions of the first mask define the shape of thepixel electrode. The first region has a semitransparent pattern, and thesecond region has an opaque pattern. Each of the first region and thesecond region consists of a plurality of sub-regions, and thesub-regions of the first region and the second region are alternatelyarranged.

[0020] In order to form the pixel electrode, a transparent conductivelayer is deposited over the bottom substrate. A photoresist film iscoated on the transparent conductive layer. The photoresist film isselectively exposed to light using the mask. A photoresist pattern isformed on the conductive layer. The photoresist pattern has a firstphotoresist portion placed over the first region of the pixel electrodewith a first thickness, and a second photoresist portion placed over thesecond region of the pixel electrode with a second thickness larger thanthe first thickness. The transparent conductive layer is etched usingthe photoresist pattern as a mask. The first photoresist portion isremoved while exposing the underlying transparent conductive layer. Thefirst region of the pixel electrode is formed through surface-treatingthe exposed portion of the transparent conductive layer. The secondphotoresist portion is removed while exposing the second region of thepixel electrode.

[0021] The surface may be treated through bombarding inert gas on theexposed portion of the transparent conductive layer, or through wetetching the exposed portion of the transparent conductive layer using awet etching solution. The firsthand the second portions, of thephotoresit pattern may be removed through dry etching.

[0022] The semiconductor pattern and the data wire are formed throughphotolithography using a photoresist pattern having different thickness.The photoresist pattern has a first photoresist portion placed over thedata wire with a first thickness, and a second photoresist portionplaced over the source and the drain electrode with a second thicknesssmaller than the first thickness.

[0023] In order to form the semiconductor pattern and the data wire, asemiconductor layer and a conductor layer are deposited on the gateinsulating layer, and the photoresist pattern is formed on theconductive layer. The conductive layer is etched using the photoresistpattern as a mask while partially exposing the semiconductor layer. Asemiconductor pattern is completed through removing the exposed portionof the semiconductor layer and the second portion of the photoresistpattern while partially exposing the conductive layer between the sourceand the drain electrode. A data wire is formed through removing theexposed portion of the conductive layer, and the first portion of thephotoresist pattern is removed. The photoresist pattern may be formedusing a mask having a first region with a predetermined lighttransmissivity, a second region with a light transmissivity lower thanthe light transmissivity of the first region, and a third region with alight transmissivity higher than the light transmissivity of the firstregion.

[0024] The step of forming the data wire may be made after thesemiconductor pattern is formed on the gate insulating layer.

[0025] In order to form the top substrate, color filters are formed on asecond insulating substrate. A common electrode is formed on thesubstrate such that the common electrode covers the color filters. Thecommon electrode may be formed in the following way. A transparentconductive layer is deposited over the second insulating substrate suchthat the transparent conductive layer covers the color filters. Aphotoresist film is located on the transparent conductive layer. Thephotoresist film is selectively exposed to light using the second mask.A photoresist pattern is formed on the transparent conductive layerthrough developing the light-exposed photoresist film. The photoresistpattern has a first portion placed over the first region of the commonelectrode with a first thickness, and a second portion placed over thesecond region of the common electrode with a second thickness largerthan the first thickness. The transparent conductive layer is etchedusing the photoresist pattern as a mask. The first portion of thephotoresist pattern is removed while ex posing the underlyingtransparent conductive layer. The first region of the common electrodeis formed through surface treating the exposed portion of thetransparent conductive layer, and the second region of the commonelectrode is formed through removing the second portion of thephotoresist pattern. The surface may be treated through bombarding inertgas on the exposed portion of the transparent conductive layer, orthrough wet etching the exposed portion of the transparent conductivelayer using a wet etching solution.

[0026] The first and the second portions of the photoresist pattern maybe removed through dry etching.

[0027] The resulting liquid crystal display includes a bottom substratewith a first region, where liquid crystal molecules bear a first pretiltangle, and a second region where liquid crystal molecules bear a secondpretilt angle larger than the first pretilt angle. A top substrate facesthe bottom substrate with liquid crystal molecules bearing a thirdpretilt angle. The third pretilt angle mediates between the first andthe second pretilt angles. A liquid crystal layer is sandwiched betweenthe bottom and the top substrates with liquid crystal molecules. Theliquid crystal molecules of the liquid crystal layer are twisted at thefirst region in a first direction while being twisted at the secondregion in a second direction.

[0028] The bottom substrate includes a gate wire, and a data wirecrossing over the gate wire while being insulated from the gate wire.Thin film transistors are electrically connected to the gate wire andthe data wire, and pixel electrode are electrically connected to thethin film transistors. Each pixel electrode bears a first surfaceroughness at the first region while bearing a second surface roughnessat the second region. The second surface roughness is higher than thefirst surface roughness.

[0029] The top substrate includes a common electrode corresponding tothe pixel electrode with a third surface roughness medium between thefirst surface roughness and the second surface roughness. An alignmentfilm on the common electrode may have grooves such that the liquidcrystal molecules close thereto bear a third pretilt angle.

[0030] According to another aspect of the present invention, in a methodfor fabricating a liquid crystal display, a bottom substrate is formedsuch that it has a first region where liquid crystal molecules bear afirst pretilt angle, and a second region where liquid crystal moleculesbear a second pretilt angle smaller than the first pretilt angle. A topsubstrate is formed such that it faces the bottom substrate with liquidcrystal molecules bearing a third pretilt angle, the third pretilt anglemedium between the first pretilt angle and the second pretilt angle. Aliquid crystal layer is formed between the bottom and the top substrateswith liquid crystal molecules. The liquid crystal molecules of theliquid crystal layer are twisted at the first region in a firstdirection while being twisted at the second region in a seconddirection.

[0031] In order to form the bottom substrate, a gate wire a data wire anothing film transistor are formed on a first insulating substrate suchthat the data wire crosses over the gate wire while being insulated fromthe gate wire, and the thin film transistors are electrically connectedto the data wire. Pixel electrode is formed such that they areelectrically connected to the thin film transistors. Each pixelelectrode bears a first surface roughness at the first region whilebearing a second surface roughness at the second region. The secondsurface roughness is higher than the first surface roughness.

[0032] In order to form the pixel electrode, a transparent conductivelayer is deposited over the top substrate. A photoresist film is coatedon the transparent conductive layer. The photoresist film isselectively, exposed to light using a mask. A photoresist pattern isformed on the transparent conductive layer through developing thelight-exposed photoresist film. The photoresist pattern has a firstportion placed over the first region of the common electrode with afirst thickness, and a second portion placed over the second region ofthe common electrode with a second thickness larger than the firstthickness. The transparent conductive layer is etched using thephotoresist pattern as a mask. The first portion of the photoresistpattern is removed while exposing the underlying transparent conductivelayer. The first region of the pixel electrode is formed throughsurface-treating the exposed portion of the transparent conductivelayer. The second region of the pixel electrode is formed throughremoving the second portion of the photoresist pattern. The surface maybe treated through bombarding inert gas on the exposed portion of thetransparent conductive layer, or through wet-etching the exposed portionof the transparent conductive layer using a wet etching solution.

[0033] The top substrate may be formed through forming a commonelectrode on a second insulating substrate such that it faces the pixelelectrode with a third surface roughness medium between the firstsurface roughness and the second surface roughness. The common electrodemay be formed through depositing a transparent conductive layer over thetop substrate, and surface-treating the transparent conductive layersuch that the transparent conductive layer bears the third surfaceroughness. The surface may be treated through bombarding inert gas onthe exposed portion of the transparent conductive layer, or throughwet-etching the exposed portion of the transparent conductive layerusing a wet etching solution.

[0034] Furthermore, the top substrate may be formed in the followingway. A common electrode is formed on a second insulating substrate suchthat the common electrode faces the pixel electrode. An alignment filmis coated over the substrate such that the alignment film covers thecommon electrode. The alignment film is rubbed such that the liquidcrystal molecules at the top substrate bear the third pretilt angle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] A more complete appreciation of the invention, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings in which like reference symbols indicate the same or thesimilar components, wherein:

[0036]FIG. 1 is a schematic sectional view of a liquid crystal displayat one pixel area according to a prior art;

[0037]FIG. 2 is a plan view of a liquid, crystal display according to afirst preferred embodiment of the present invention;

[0038]FIGS. 3 and 4 are cross sectional views of the liquid crystaldisplay taken along the II-II′ line and the III-III′ line of FIG. 2,respectively;

[0039]FIGS. 5A through 17B sequentially illustrate the steps offabricating the liquid crystal display shown in FIG. 2;

[0040]FIGS. 18A, 18B and 18C illustrate mask patterns used forfabricating the liquid crystal display shown in FIG. 2;

[0041]FIG. 19 is a plan view of a liquid crystal display according to asecond preferred embodiment of the present invention;

[0042]FIG. 20 is a cross sectional view of the liquid crystal displaytaken along the XX-XX′ line of FIG. 19;

[0043]FIGS. 21A through 29 sequentially illustrate the steps offabricating the liquid crystal display shown in FIG. 19;

[0044]FIGS. 30 and 31 are sectional views of a liquid crystal displayaccording to a third preferred embodiment of the present invention; and

[0045]FIG. 32 is a sectional view of a liquid crystal display accordingto a fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Preferred embodiments of this invention will be explained withreference to the accompanying drawings.

[0047]FIG. 2 is a plan view of a liquid crystal display according to afirst preferred embodiment of the present invention, and FIGS. 3 and 4are cross sectional views of the liquid crystal display taken along theII-II′ line and the III-III′ line of FIG. 2, respectively.

[0048] Gate wires, are formed on an insulating substrate 10. Each gatewire includes gate line 22 proceeding in the horizontal direction, gatepad 24, gate electrode 26, and storage capacitor electrode 28. Thestorage capacitor electrode 28 proceeds in parallel with the gate line22 to receive common voltages from the outside.

[0049] The storage capacitor electrode 28 is overlapped with a storagecapacitor conductive pattern 68 connected to pixel electrode 82 to bedescribed later to thereby form storage capacitor for enhancing theelectric potential storage capacity of the pixels. In case a sufficientstorage capacity is obtained with the overlapping of the pixel electrode82 and the gate line 22, the storage capacitor electrode 28 may beomitted.

[0050] The gate wire may be formed with a single-layered structure, or amultiple-layered structure. It is preferable that the gate wires areformed with a low resistance metallic material. In a single-layeredstructure, the gate wire may be formed with a metallic material based onchrome or chrome alloy, molybdenum or molybdenum alloy, aluminum oraluminum alloy, or, silver or silver alloy. In a double-layeredstructure, at least one layer may be formed with a low resistancemetallic material.

[0051] A gate insulating layer 30 is formed on the substrate 10 with aninsulating material such as silicon nitride such that it covers the gatewire.

[0052] Semiconductor patterns 42 and 48 formed with amorphous siliconare formed on the gate insulating layer 30, and ohmic contact patterns55, 56 and 58 formed with impurities doped amorphous silicon are formedon the semiconductor patterns 42 and 48.

[0053] A data wire is formed on the ohmic contact patterns 55, 56 and.58. Each data wire includes data line 62 proceeding in the verticaldirection, data pad 64, source and drain electrodes 65 and 66 for thinfilm transistors, and a storage capacitor conductive pattern 68 placedover the storage capacitor electrode 28.

[0054] The data wire may be formed with a single-layered structure, or amultiple-layered structure. It is preferable that the data wires areformed with a low resistance metallic material. In a single-layeredstructure, the data wire may be formed with a metallic material based onchrome or chrome alloy, molybdenum or molybdenum alloy, aluminum oraluminum alloy, or, silver or silver alloy. In a double-layeredstructure, at least one layer may be formed with a low resistancemetallic material.

[0055] The semiconductor patterns 42 and 48 comprise a portion for thinfilm transistor 42, and a portion for storage capacitor 48. Thesemiconductor patterns 42 and 48 have the same shape as the data wireand the ohmic contact patterns except for the channel region between thesource and the drain electrodes 65 and 66. That is, the storagecapacitor semiconductor pattern 48 has the same shape as the storagecapacitor conductive pattern 68 or the storage capacitor ohmic contactpattern 58. The thin film transistor semiconductor pattern 42 has thesame shape as the data line 62, the data pad 64, and the source anddrain electrodes 65 and 66 except that it continuously proceeds at thechannel region between the source and the drain electrodes 65 and 66without separation.

[0056] The ohmic contact patterns 55, 56 and 58 lower the contactresistance between the underlying semiconductor patterns 42 and 48 andthe overlying data wire while bearing the same shape as the data wire.The ohmic contact patterns 55, 56 and 58 is formed with a first portion55 contacting the data line 62, the data pad 64 and the source electrode65, a second portion 56 contacting the drain electrode 66, and a thirdportion 58 contacting the storage capacitor conductive pattern 68.

[0057] A protective layer 70 is formed on the resultant substratecomprising the data wire to cover the data wire. The protective layer 70is formed with an, inorganic insulating material such as siliconnitride, or an organic material such as benzocyclobutene (BCB).

[0058] The protective layer 70 is provided with first contact hole 72exposing the drain electrode 66, second contact hole 74 exposing thegate pad 24 together with the gate insulating layer 30, and thirdcontact hole 76 exposing the data pad 64. Furthermore, fourth contacthole 78 is formed in the protective layer 70 to expose the storagecapacitor conductive pattern 68.

[0059] Pixel electrode 82 connected to the drain electrode 66 throughthe first contact hole 72, and subsidiary gate and data pads 84 and 86connected to the gate and the data pads 24 and 64 through the second andthe third contact holes 74 and 76 are formed on the protective layer 70.The pixel electrode 82 is also connected to the storage capacitorconductive pattern 68 through the fourth contact hole 78 to transmitpicture signals to the storage capacitor conductive pattern 68.

[0060] The pixel electrode 82 is formed with a transparent conductivematerial such as indium tin oxide (ITO) and indium zinc oxide (IZO).

[0061] One side of the pixel electrode 82 with respect to the centerline 100 is patterned to have a rough surface. The portion of the pixelelectrode 82 with a rough surface will be hereinafter referred to as thefirst pixel electrode region 82 a, and the other portion of the pixelelectrode 82 with a smooth surface as the second pixel electrode region82 b.

[0062] As mentioned, the surface roughness of the pixel electrode 82 isrelated to the pretilt angles of the liquid crystal molecules. Thepretilt angle of the liquid crystal molecules at the first pixelelectrode region 82 a is small, whereas the pretilt angle thereof at thesecond pixel electrode region 82 b is large.

[0063] As shown in FIG. 3, a common electrode 112 is formed at the topsubstrate 110 and corresponds to the pixel electrode 82. The one portionof the common electrode 112 has a smooth surface, being referred to asthe first common electrode region 112 a and the other portion of thecommon electrode 112 also has a rough surface, being referred to as thesecond common electrode region 112 b. The first common electrode region112 a corresponds to the first pixel electrode region 82 a, and thesecond common electrode region 112 b corresponds to the second pixelelectrode region 82 b. The pretilt angle of the liquid crystal moleculesat the first common electrode region 112 a is large, and the pretiltangle thereof at the second common electrode region 112 b is small.

[0064] The liquid crystal molecules 151 interposed between the firstpixel electrode region 82 a bearing a small pretilt angle and the firstcommon electrode region 112 a bearing a large pretilt angle are twistedin the first direction 1 pursuant to the pretilt angle of the firstcommon electrode region 112 a to thereby form a first liquid crystaldomain. By contrast, the liquid crystal molecules 152 interposed betweenthe second pixel electrode region 82 b bearing a large pretilt angle andthe second common electrode region 112 b bearing a small pretilt angleare twisted in the second direction 2 pursuant to the pretilt angle ofthe second pixel electrode region 82 b to thereby form a second liquidcrystal domain. That is, two liquid crystal domains that are twisted indifferent directions are present at one pixel area.

[0065] In one pixel region, the liquid crystal molecules at apredetermined region of the bottom substrate bear a large pretilt angle,and those at the corresponding region of the top substrate bear a smallpretilt angle, whereas the liquid crystal molecules at another region ofthe bottom substrate bear a small pretilt angle, and those at thecorresponding region of the top substrate bear a large pretilt angle. Inthis way, a multi domain structure is formed in one pixel regionpursuant to the different pretilt angles of the liquid crystal moleculesat the top and the bottom substrates, serving to improve wide viewingangle characteristic of the resulting display device.

[0066] A method for fabricating a bottom substrate for the liquidcrystal display will be now explained with reference to FIGS. 5A, 5B,5C, 6A, 6B, 6C, 7A, 7B, 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B, 11C, 12A,12B, 12C, 13A, 13B, 14, 15A, 15B, 16A, 16B, 17A AND 17B and FIGS. 2, 3and 4.

[0067] As shown in FIGS. 5A through 5C, a gate wire is formed on aninsulating substrate 10 through depositing a low resistance metalliclayer on the insulating substrate 10 and patterning the deposited layerthrough photolithography. The gate wire includes gate line 22, gate pad24, gate electrode 26, and storage capacitor electrode 28.

[0068] Alternatively, two or more metallic layers may be deposited onthe substrate and patterned to thereby form a gate wire with amultiple-layered structure.

[0069] Thereafter, as shown in FIGS. 6A through 6C, a gate insulatinglayer 30 is formed on the gate wire, and semiconductor patterns 42 and48, ohmic contact patterns 55, 56 and 58 and a data wire are formed onthe gate insulating layer 30.

[0070] The data wire includes data line 62, data pad 64, sourceelectrode 65, drain electrode 66, and a storage capacitor conductivepattern 68.

[0071] The ohmic contact patterns 55, 56 and 58 placed under the datawire has the same shape as the data wire, and the semiconductor patterns42 and 48 placed under the ohmic contact patterns 55, 56 and 58 have aportion for thin film transistors 42, and a portion for storagecapacitors 48. The thin film transistor semiconductor pattern 42 has thesame shape as the data line 62, the data pad 64, and the source anddrain electrodes 65 and 66 except that it continuously proceeded at thechannel region between the source and the drain electrode 65 and 66without separation.

[0072] The data wire, the ohmic contact patterns 55, 56 and 58, and thesemiconductor patterns 42 and 48 may be formed using one mask. Thistechnique will be now explained with reference to FIGS. 7A through 10B.

[0073] As shown in FIGS. 7A and 7B, a gate insulating layer 30, asemiconductor layer 40, and an impurity-doped semiconductor layer 50 aresequentially deposited on the resultant substrate comprising the gatewire through chemical vapor deposition. Subsequently, a low resistancemetallic layer 60 is deposited on the doped semiconductor layer 50, anda photoresist film is coated on the metallic layer 60.

[0074] The photoresist film is then exposed to light, and developed tothereby form a photoresist pattern 112 and 114. The photoresist patternhas a first portion 112 placed over the data wire area A with apredetermined thickness, and a second portion 114 placed over thechannel area C between the source and the drain electrode 65 and 66 witha thickness smaller than the thickness of the first portion 112. Thephotoresist film over the remaining area B is all removed. The thicknessratio of the second photoresist portion 114 to the first portion 112 maybe controlled depending upon subsequent processing conditions. It ispreferable that the thickness of the second photoresist portion 114 maybe half or less of the thickness of the first photoresist portion 112.

[0075] Such a photoresist pattern having portions of different thicknessmay be formed with a mask having portions with different lighttransmission. Slit pattern, lattice pattern or a semitransparent film isusually formed in the mask to control the light transmission.

[0076] In the case of using slit pattern or lattice pattern, thedistance between one pattern and other pattern is established to besmaller than the resolution of a light exposing device. In the case ofusing a semitransparent film, thin film having portions of differentthickness or light transmissivity may be used to control the lighttransmission.

[0077] When the photoresist film is exposed to light through such amask, the molecules of the photoresist film at the B area directlyexposed to light are completely decomposed, the molecules of thephotoresist film at the C area corresponding to the slit pattern or thesemitransparent film are decomposed at some degree and the molecules atthe A area covered by the light interception film of the mask are barelydecomposed. At this time, if the light exposing period of time is toolong, all of the molecules of the photoresist film may be decomposed.Therefore, the light exposing time should be controlled in anappropriate manner.

[0078] When the selectively light-exposed photoresist film is developed,the resulting photoresist pattern has different thickness depending uponthe molecular decomposition degrees.

[0079] Thereafter, as shown in FIGS. 8A and 8B, using the photoresistpattern 112 and 114 as a mask, the metallic layer 60 exposed at the Barea is removed. Consequently, the conductive pattern 67 and 68 at thechannel area C and the data wire area A is left over, and the conductivelayer at the remaining area B is removed while exposing the underlyingdoped semiconductor layer 50.

[0080] The conductive patterns have a portion for storage capacitor 68,and a portion for the data wire 67 where the source and the drainelectrode 65 and 66 are not yet separated.

[0081] As shown in FIGS. 9A and 9B, the doped semiconductor layer 50exposed at the B area, and the underlying semiconductor layer 40 aresimultaneously removed together with the second photoresist portion 114through dry etching. The etching should be made in condition that thephotoresist pattern 112 and 114, the doped semiconductor layer 50 andthe semiconductor layer 40 are simultaneously etched while not etchingthe gate insulating layer 30. Particularly, it is preferable that theetching ratios with respect to the photoresist pattern 112 and 114 andthe semiconductor layer 40 are the same. For instance, when a mixture ofSF₆ and HCl, or SF₆ and O₂ is used for the etching gas, the photoresistpattern 112 and 114 and the semiconductor layer 40 can be etched bynearly the same thickness.

[0082] When the etching ratios with respect to the photoresist pattern112 and 114 and the semiconductor layer 40 are the same, the thicknessof the second photoresist portion 114 should be the same as or less thanthe sum in thickness of the semiconductor layer 40 and the dopedsemiconductor layer 50.

[0083] Consequently, the second photoresist portion 114 at the channelarea C is removed while exposing the conductive pattern 67, and thedoped semiconductor layer 50 and the semiconductor layer 40 at area Bare removed while exposing the underlying gate insulating layer 30.Meanwhile, the first photoresist portion 112 at the data wire area A isalso etched while being reduced in thickness.

[0084] In this step, the semiconductor pattern with a portion for thinfilm transistor 42, and a portion for storage capacitor 48 is completed.

[0085] At this time, the ohmic contact pattern 57 for the thin filmtransistors has the same shape as the underlying thin film transistorsemiconductor pattern 42, and the ohmic contact pattern 58 for storagecapacitors has the same shape as the underlying storage capacitorsemiconductor pattern 48.

[0086] Thereafter, the second photoresist portion 114 on the conductivepattern 67 at the channel area C is removed through ashing.

[0087] As shown in FIGS. 10A and 10B, the conductive pattern 67 and theunderlying ohmic contact pattern 57 at the channel area C are etchedusing the remaining first photoresist portion 112 as a mask.

[0088] At this time, the semiconductor pattern 42 as well as the firstphotoresist portion 112 may be partially etched while being reduced inthickness. The etching should be made in condition that the gateinsulating layer 30 is not etched. It is preferable that the photoresistpattern should be so thick as not to expose the underlying data wirethrough the etching.

[0089] As a result, source electrode 65 and drain electrode 66 arecompleted from the conductive pattern 67 together with data line 62, andthe underlying ohmic contact patterns 55, 56 and 58 are completed.

[0090] Finally, the first photoresist portion 112 left at the data wirearea A is removed through ashing, thereby resulting in the sectionalstructure shown in FIGS. 6B and 6C.

[0091] As shown in FIGS. 11A, 11B and 11C, a protective layer 70 isformed on the resultant substrate comprising the data wire throughdepositing a silicon nitride layer or coating an organic insulatinglayer.

[0092] The protective layer 70 and the gate insulating layer 30 areetched through photolithography to thereby form first, second and thirdcontact hole 72, 76 and 78 exposing the drain electrode 66, the data pad64 and the storage capacitor conductive pattern 68, respectively, andfourth contact hole 74 exposing the gate pad 24.

[0093] Then, as shown in FIGS. 12A, 12B and 12C a transparent conductivelayer based on ITO or IZO is deposited on the resultant substratecomprising the protective layer 70 and patterned throughphotolithography to thereby form pixel electrode 82 connected to thedrain electrode 66 and the storage capacitor conductive pattern 68, andsubsidiary gate and data pads 84 and 86 connected to the gate and thedata pad 24 and 64.

[0094] At this time, the pixel electrode 82 has different surfaceroughness. For instance, the pixel electrode 82 is patterned such thatit is divided into two regions with respect to the center line 100. Thatis, the pixel electrode 82 may be divided into a first pixel electroderegion 82 a with a rough surface, and a second pixel electrode region 82b with a smooth surface.

[0095] Such a pixel electrode may be formed using one mask. Thistechnique will be now explained with reference to FIGS. 13A through 17B.

[0096] As shown in FIGS. 13A and 13B, a transparent conductive layer 80based on ITO or IZO is deposited on the resultant substrate comprisingthe protective layer 70, and a photoresist film is coated on thetransparent conductive layer 80.

[0097] The photoresist film is exposed to light through a mask, anddeveloped to thereby form a photoresist pattern 212 and 214. Thephotoresist pattern has a first photoresist portion 212 placed over thegate pad 84, the data pad 86 and the second pixel electrode region 82 bhaving a smooth surface, and a second photoresist portion 214 placedover the first pixel electrode region 82 a having a rough surface. Thephotoresist film at the remaining area B is all removed.

[0098] Such a photoresist pattern having portions of different thicknessmay be formed with a mask having portions with different lighttransmission. Slit pattern, lattice pattern or a semitransparent film isusually formed in the mask to control the light transmission. In theslit pattern or lattice pattern, the distance between one pattern andother pattern is established to be smaller than the resolution of alight exposing device. In a semitransparent film, thin film havingportions of different thickness or light transmissivity may be used tocontrol the light transmission. Such a mask can be fabricated in the waypreviously described with reference to FIGS. 7A and 7B.

[0099]FIG. 14 illustrates a mask 200 used in forming the pixel electrode82 where the data wires of the bottom substrate overlapped with the mask200 are indicated by faint lined patterns.

[0100] The mask 200 has a slit or lattice pattern 200 a to be placed atthe first pixel electrode region 82 a to reduce the amount of lightilluminated thereto, an opaque pattern 200 b to be placed at the secondpixel electrode region 82 b to block the light, and a transparentpattern to be placed at the non-pixel electrode area to entirely exposethe area to light.

[0101] As described earlier, the amount of light transmission can becontrolled through varying the opening width or distance at the slit orlattice pattern. When the photoresist film is exposed to light throughsuch a mask, the molecules of the photoresist film at the B areadirectly exposed to light are completely decomposed, the molecules ofthe photoresist film at the C area corresponding to the slit pattern orthe semitransparent film are decomposed to some degree, and themolecules of the photoresist film at the A area blocked by the lightinterception film are barely decomposed.

[0102] When the selectively exposed photoresist film is developed, theresulting photoresist film has portions of different thickness dependingupon the molecular decomposition degrees.

[0103] As shown in FIGS. 15A and 15B, the transparent conductive film 80is etched using the photoresist pattern 212 and 214 as a mask to therebyform pixel electrode 82, subsidiary gate pad 84 connected to the gatepad 24, and subsidiary data pad 86 connected to the data pad 64. Theportion of the transparent conductive film 80 entirely exposed to lightis removed.

[0104] Thereafter, as shown in FIGS. 16A and 16B, the photoresistpattern 212 and 214 is dry-etched such that the second photoresistportion 214 is removed. At this time, O₂ may be used for the etchinggas. In this, process, the second photoresist portion 214 is removed,and the first photoresist portion 212 also reduces its thickness as muchas the thickness of the second photoresist portion 214.

[0105] When the second photoresist portion 214 is removed, the portionof the pixel electrode 82 to be the first pixel electrode region 82 a isexposed to the outside.

[0106] As shown in FIGS. 17A and 17B, the exposed portion of the pixelelectrode 82 is surface-treated to make the surface rough. In order toroughen the surface, the following technique may be used.

[0107] First, inert gas such as argon, neon and crypton may bephysically bombarded on the surface of the first pixel electrode region82 a to partially remove the surface of the pixel electrode 82. In thiscase, the period of time of using the inert gas or the energy ofinjecting the inert gas should be appropriately controlled to obtain thedesired roughness of the surface.

[0108] Second, the resultant substrate shown in FIGS. 16A and 16B may bedipped into an etching a solution for a predetermined period of time toetch the transparent conductive layer in chemical reaction with thetransparent conductive layer and the etching solution. In this case, itis preferable that the concentration of the etching solution, or thetime period for the dipping should be appropriately controlled to obtainthe desired roughness of the surface.

[0109] Then, the remaining first photoresist portion 212 is removed toexpose the underlying second pixel electrode region 82 b with a smoothsurface. Consequently, as shown in FIGS. 12B and 12C; the pixelelectrode 82 having the first pixel electrode region 82 a with a roughsurface and the second pixel electrode region 82 b with a smooth surfaceis completed.

[0110] In this way, the pixel electrode 82 with different surfaceroughness, can be formed using one mask.

[0111] A top substrate corresponding to the above-structured bottomsubstrate can be formed in the following way.

[0112] Color filters (not shown) are formed on an insulating substrate110, and a common electrode 112 based on ITO or IZO covers the colorfilters. As with the pixel electrode 82, the common electrode 112 isalso patterned such that the surface thereof becomes to be partiallyrough. The surface roughness of the common electrode 112 symmetricallycorresponds to that of the pixel electrode 82. That is, the commonelectrode 112 has a first common electrode region 112 a with a smoothsurface that corresponds to the first pixel electrode region 82 a with arough surface, and a second common electrode region 112 b with a roughsurface that corresponds to the second pixel electrode region 82 b witha smooth surface. Therefore, the first common electrode region 112 abears are large pretilt angles, whereas the second common electroderegion 112 b bears a small pretilt angle.

[0113] Such a common electrode 112 can be also formed using one mask inthe same way as forming the pixel electrode 82.

[0114] Alignment films (not shown) are coated over the top substrate andthe bottom substrate, respectively. Then, the two substrates areassembled together, and a liquid crystal is injected between thesubstrates to thereby fabricate the liquid crystal display shown inFIGS. 3 and 4.

[0115] The liquid crystal molecules 151 interposed between the firstpixel electrode region 82 a bearing a small pretilt angle and the firstcommon electrode region 112 a bearing a large pretilt angle are twistedin the first direction 1 to thereby form a first liquid crystal domain.The liquid crystal molecules 152 interposed between the second pixelelectrode region 82 b bearing a large pretilt angle and the secondcommon electrode region 112 b bearing a small pretilt angle are twistedin the second direction 2 to thereby form a second liquid crystaldomain. Consequently, two liquid crystal domains are present within onepixel region.

[0116] As described above, in one pixel region, the liquid crystalmolecules at a predetermined region of the bottom substrate bear a largepretilt angle, and those at the corresponding region of the topsubstrate bear a small pretilt angle, whereas the liquid crystalmolecules at another region of the bottom substrate bear a small pretiltangle, and those at the corresponding region of the top substrate bear alarge pretilt angle. In this way, a multi domain structure is formed inone pixel region pursuant to the different pretilt angles of the liquidcrystal molecules at the top and the bottom substrates, serving toimprove wide viewing angle characteristic of the resulting displaydevice.

[0117] Furthermore, the mask for forming the pixel electrode may bearthe patterns shown in FIGS. 18A, 18B and 18C. Those figures illustratesamples of the mask patterns for the pixel electrode area.

[0118] The mask pattern to be placed over the pixel electrode area maybe quadruple-partitioned in horizontal and vertical directions whilealternately placing the semitransparent pattern portion 200 a and theopaque pattern portion 200 b side by side.

[0119] The semitransparent pattern portion 200 a may be formed with aslit pattern. When the slit pattern proceeds in the horizontaldirection, a mask shown in FIG. 18A may be produced. When the slitpattern proceeds in the inclined direction, a mask shown in FIG. 18B maybe produced. Furthermore, in case the semitransparent pattern portion200 a is formed with a lattice pattern, a mask shown in FIG. 18C may beproduced.

[0120] When the pixel electrode are patterned using the masks shown inFIGS. 18A, 18B and 18C, four liquid crystal domains can be formed in onepixel region. Of course, in this case, the common electrode is alsopatterned such that its patterns correspond inversely to the pixelelectrode patterns.

[0121]FIG. 19 is a plan view of a liquid crystal display according to asecond preferred embodiment of the present invention, and FIG. 20 is across sectional view of the liquid crystal display taken along theXX-XX′ line of FIG. 19.

[0122] A gate wire is formed on an insulating substrate 10. The gatewire includes gate line 22 proceeding in the horizontal direction, gatepad 24, and gate electrode 26.

[0123] The gate wire may be formed with a single-layered structure, or amultiple-layered structure. It is preferable that the gate wires areformed with a low resistance metallic material. In a single-layeredstructure, the gate wire may be formed with a metallic material based onchrome or chrome alloy, molybdenum or molybdenum alloy, aluminum oraluminum alloy, or, silver or silver alloy. In a double-layeredstructure, at least one layer may be formed with a low resistancemetallic material.

[0124] A gate insulating layer 30 is formed on the substrate 10 with thegate wire using an insulating material such as silicon nitride.

[0125] A semiconductor pattern 42 consisting of semiconductor materialsuch as amorphous silicon is formed on the gate insulating layer 30 tooverlap the gate electrode 26. Ohmic contact patterns 55 and 56consisting of impurity-doped semiconductor are formed on thesemiconductor pattern 42.

[0126] A data wire is formed on the ohmic contact pattern 55 and 56 andthe gate insulating layer 30. The data wire includes data line 62, datapad 64, source electrode 65 branched from the data line 62 to form thinfilm transistor and contacting one portion of the ohmic contact pattern55, and drain electrode 66 facing the source electrode 65 to form thethin film transistors while contacting the opposite-side portion 56 ofthe ohmic contact pattern.

[0127] The data wire may be formed with a single-layered structure, or amultiple-layered structure. It is preferable that the data wire should,be formed with a low resistance metallic material. In a single-layeredstructure, the data wire may be formed with a metallic material such aschrome, molybdenum, aluminum, and silver. In a double-layered structure,at least one layer should be formed with a low resistance metallicmaterial.

[0128] A protective layer 70 is formed on the substrate 10 with an inorganic insulating material such as silicon nitride or an organicinsulating material such as benzocyclo butene (BCB) while covering thedata wire

[0129] The protective layer 70 is provided with first contact hole 72exposing the drain electrode 66, second contact hole 74 exposing thegate pad 24 together with the gate insulating layer 30, and thirdcontact hole 76 exposing the data pad 64.

[0130] Pixel electrode 82 connected to the drain electrode 66 throughthe first contact hole 72, and subsidiary gate and data pad 84 and 86connected to the gate and the data pad 24 and 64 through the second andthe third contact hole 74 and 76.

[0131] The pixel electrode 82 may be formed with a transparentconductive material such as ITO or IZO.

[0132] The pixel electrode 82 is patterned such that the one-sidedportion with respect to the center line 100 has a rough surface. Thatis, the pixel electrode 82 has a first pixel electrode region 82 a witha rough surface, and a second pixel electrode region 82 b with a smoothsurface.

[0133] As described earlier, the surface roughness of the pixelelectrode 82 is related to the pretilt angles of the liquid crystalmolecules. The first pixel electrode region 82 a with a rough surfacebears a small pretilt angle, whereas the second pixel electrode region82 b with a smooth surface bears a large pretilt angle.

[0134] A common electrode 112 corresponding to the pixel electrode 82 isformed at a top substrates 110. As shown in FIG. 20, the surfaceroughness of the common electrode 112 is symmetrical to that of thepixel electrode 82. That is, the common electrode 112, has a firstcommon electrode region 112 a with a smooth surface that corresponds tothe first pixel electrode region 82 a with a rough surface, and a secondcommon electrode region 112 b with a rough surface that corresponds tothe second pixel electrode region 82 b with a smooth surface. Therefore,the first common electrode region 112 a bears a large pretilt angle,whereas the second common electrode region 112 b bears a small pretiltangle.

[0135] The liquid crystal, molecules 151 interposed between the firstpixel electrode region 82 a bearing a small pretilt angle and the firstcommon electrode region 112 a bearing a large pretilt angle are twistedin the first direction 1 pursuant to the pretilt angle of the firstcommon electrode region 112 a to thereby form a first liquid crystaldomain. By contrast, the liquid crystal molecules 152 interposed betweenthe second pixel electrode region 82 b bearing a large pretilt angle andthe second common electrode region 112 b bearing a small pretilt angleare twisted in the second direction 2 pursuant to the pretilt angle ofthe second pixel electrode region 82 b to thereby form a second liquidcrystal domain. That is, two liquid crystal domains that are twisted indifferent directions are present in one pixel region.

[0136] As described above, in one pixel region, the liquid crystalmolecules at a predetermined region of the bottom substrate bear a largepretilt angle, and those at the corresponding region of the topsubstrate bear a small pretilt angle, whereas the liquid crystalmolecules at another region of the bottom substrate bear a small pretiltangle, and those at the corresponding region of the top substrate bear alarge pretilt angle. In this way, a multi domain structure is formed inone pixel region pursuant to the different pretilt angles of the liquidcrystal molecules at the top substrate and the bottom substrate, servingto improve wide viewing angle characteristic of the resulting displaydevice.

[0137] A method for fabricating the bottom substrate will be nowexplained with reference to FIGS. 21A, 21B, 22A, 22B, 23A, 23B, 24A,24B, 25A, 25B, 26, 27, 28 and 29.

[0138] As shown in FIGS. 21A and 21B, a low resistance metallic layer isdeposited on an insulating substrate 10, and etched throughphotolithography to thereby form a gate wire. The gate wire includesgate line 22, gate pad 24, and gate electrode 26.

[0139] At this time, two or more metallic layers may be deposited on thesubstrate 10, and etched through photolithography to thereby form a gatewire with a multiple-layered structure.

[0140] Thereafter, as shown in FIGS. 22A and 22B, a gate insulatinglayer 30, a semiconductor layer, and an impurity-doped semiconductorlayer are sequentially deposited over the resultant substrate comprisingthe gate wire. The doped semiconductor layer, and the semiconductorlayer are etched through photolithography to thereby form anisland-shaped semiconductor pattern 42, and an ohmic contact pattern 52.

[0141] Then, as shown in, FIGS. 23A and 23B, a low resistance, metalliclayer is deposited over the resultant substrate, and etched to therebyform a data wire. The data wire includes data line 62, data pad 64,source electrode 65, and drain electrode 66.

[0142] The island-shaped ohmic contact pattern 52 is etched using thesource and the drain electrode 65 and 66 as a mask to thereby form afirst ohmic contact pattern portion 55 contacting the source electrode65, and a second ohmic contact pattern portion 56 contacting the drainelectrode 66.

[0143] As shown in FIGS. 24A and 24B, a silicon nitride layer or anorganic insulating layer is deposited over the resultant substratecomprising the data wire to thereby form a protective layer 70.

[0144] First and third contact holes 72 and 76 are formed at theprotective layer 70 such that they expose the drain electrode 66 and thedata pad 64, and simultaneously, second contact hole 74 are formed atthe protective layer 70 and the gate insulating layer 30 such that theyexpose the gate pad 24.

[0145] As shown in FIGS. 25A and 25B, a transparent conductive layerbased on ITO or IZO is deposited over the resultant substrate, andpatterned through photolithography to thereby form pixel electrode 82connected to the drain electrode 66, and subsidiary gate and data pads84 and 86 connected to the gate and the data pads 24 and 64.

[0146] The pixel electrode 82, has portions of different surfaceroughness. For instance, the pixel electrode 82 is patterned such thatit is divided into two regions with respect to the center line 100. Thatis, thee pixel electrode 82 has first pixel electrode region 82 a with arough surface and a second pixel electrode region 82 b with a smoothsurface.

[0147] Such a pixel electrode may be formed using one mask. Thistechnique will be now explained with reference to FIGS. 26 through 29.

[0148] As shown in FIG. 26, a transparent conductive layer 80 based onITO or IZO is deposited on the resultant substrate comprising theprotective layer 70, and a photoresist film is coated on the transparentconductive layer 80.

[0149] Thereafter, the photoresist film is exposed to light through amask, and developed to thereby form a photoresist pattern 212 and 214.At this time, the photoresist pattern has a first photoresist portion212 placed over the gate pad 84, the data pad 86 and the second pixelelectrode region 82 b to bear a smooth surface, with a predeterminedthickness, and a second photoresist portion 214 placed over the firstpixel electrode region 82 a to bear a rough surface with a thicknesssmaller than that of the first photoresist portion 212. The photoresistfilm over the remaining area is all removed.

[0150] Such a photoresist pattern having portions with differentthickness may be formed with a mask having portions of different lighttransmission. Slit pattern, lattice pattern or a semitransparent film isusually formed in the mask to control the light transmission. In thecase of using slit pattern or lattice pattern, the distance between onepattern and other pattern is established to be smaller than theresolution of a light exposing device. In the case of using asemitransparent film, thin film having portions of different thicknessor light transmissivity may be used to control the light transmission.Such a mask can be fabricated in the way previously described withreference to FIG. 14.

[0151] The mask 200 has a slit or lattice pattern 200 a to be placed atthe first; pixel electrode region 82 a to reduce the amount of lightilluminated thereto, an opaque pattern 200 b to be placed at the secondpixel electrode region 82 b to block the pass of the light, and atransparent pattern to be placed at the non-pixel electrode area toentirely expose the area to light.

[0152] As described earlier, the amount of light transmission can becontrolled through varying the opening width or distance of the slit orlattice pattern. When the photoresist film is exposed to light throughsuch a mask, the molecules of the photoresist film at the B areadirectly exposed to light are completely decomposed, the molecules ofthe photoresist film at the C area corresponding to the slit pattern orthe semitransparent film are decomposed at some degree, and themolecules of the photoresist film at the A area blocked by the lightinterception film are barely decomposed.

[0153] When the selectively light-exposed photoresist film is developed,the resulting photoresist film has portions with different thicknessdepending upon the molecular decomposition degrees.

[0154] As shown in FIG. 27, the transparent conductive layer 80 isetched using the, photoresist pattern 212 and 214 as a mask to therebyform pixel electrode 82, subsidiary gate pad 84 connected to the gatepad 24, and subsidiary data pad 86 connected to the data pad 64. Theportion of the transparent conductive layer 80 entirely exposed to lightis removed.

[0155] Thereafter, as shown in FIG. 28, the photoresist pattern 212 and214 is dry-etched such that the second photoresist portion 214 isremoved. At this time O₂ may be used for the etching gas. In thisprocess, the second photoresist portion 214 is removed, and the firstphotoresist portion 212 is reduced in thickness as much as the thicknessof the second photoresist portion 214.

[0156] When the second photoresist portion 214 is removed, the portionof the pixel electrode 82 to be formed as the first pixel electroderegion 82 a is exposed to the outside.

[0157] As shown in FIG. 29, the exposed portion of the pixel electrode82 is surface-treated to roughen the surface. In order to make such asurface treatment, the following technique may be used.

[0158] First, inert gas such as argon, neon and crypton may bephysically bombarded on the first pixel electrode region 82 a topartially remove the surface of the pixel electrode 82. In this case, itis preferable that the time period for using the inert gas or the energyof injecting the inert gas should be controlled to obtain the desiredroughness.

[0159] Second, the substrate shown in FIG. 28 may be dipped into anetching solution for a predetermined period of time to thereby etch thetransparent conductive layer in chemical reaction with the etchingsolution. In this case, the concentration of the etching solution or thetime period for the dipping should be appropriately controlled to obtainthe desired roughness.

[0160] Then, the remaining first photoresist portion 212 is removedwhile exposing the underlying second pixel electrode region 82 b with asmooth surface. Consequently, as shown in FIG. 24, the pixel electrode82 having the first pixel electrode region 82 a with a rough surface andthe second pixel electrode region 82 b with a smooth surface iscompleted.

[0161] In this way, the pixel electrode 82 having portions withdifferent surface roughness can be formed using one mask.

[0162] A top substrate corresponding to the above-structured bottomsubstrate can be formed in the following way.

[0163] Color filters (not shown) are formed on an insulating substrate110, and a common electrode 112 based on ITO or IZO covers the colorfilters. As with the pixel electrode 82, the common electrode 112 isalso patterned to partially roughen its surface. The surface roughnessof the common electrode 112 symmetrically corresponds to that of thepixel electrode 82. That is, the common electrode 112 has a first commonelectrode region 112 a with a smooth surface that corresponds to thefirst pixel electrode region 82 a with a rough surface, and a secondcommon electrode region 112 b with a rough surface that corresponds tothe second pixel electrode region 82 b with a smooth surface. Therefore,the first common electrode region 112 a bears a large pretilt angle,whereas the second common electrode region 112 b bears a small pretiltangle.

[0164] Such a common electrode 112 can be also formed using one mask inthe same way as forming the pixel electrode 82.

[0165] Alignment layers (not shown) are coated over the top substrateand the bottom substrate, respectively. Then, the two substrates areassembled together, and a liquid crystal is injected between thesubstrates to thereby fabricate the liquid crystal, display shown inFIG. 20.

[0166] The liquid crystal molecules 151 interposed between the firstpixel electrode region 82 a bearing a small pretilt angle and the firstcommon electrode region 112 a bearing a large pretilt angle are twistedin the first direction 1 to thereby form a first liquid crystal domain.The liquid crystal molecules 152 interposed between the second pixelelectrode region 82 b bearing a large pretilt angle and the secondcommon electrode region 112 b bearing a small pretilt angle are twistedin the second direction 2 to thereby form a second liquid crystaldomain. Consequently, two liquid crystal domains are present in onepixel region.

[0167] As described above, the liquid crystal molecules at apredetermined region of the bottom substrate within one pixel area beara large pretilt angle, and those at the corresponding region of the topsubstrate bear a small pretilt angle, whereas the liquid crystalmolecules at another region of the bottom substrate within the pixelarea bear a small pretilt angle, and those at the corresponding regionof the top substrate bear a large pretilt angle. In this way, a multidomain structure is formed at one pixel area pursuant to the differentpretilt angles of the liquid crystal molecules at the top substrate andthe bottom substrate, serving to improve wide viewing anglecharacteristic of the resulting display device.

[0168] Alternatively, it may be proposed that the liquid crystal,molecules at a predetermined, region of the bottom substrate bear alarge pretilt angle, and those at another region of the bottom substratewithin the pixel area bear a small pretilt angle, whereas all of theliquid crystal molecules at the top substrate within the correspondingpixel area bear a pretilt angle being medium between the large pretiltangle and the small pretilt angle. In this case, a multi domainstructure is also formed at one pixel area pursuant to the differentpretilt angles of the liquid crystal molecules at the top and bottomsubstrates.

[0169] This structure will be now explained in relation to third andfourth preferred embodiments of the present invention.

[0170]FIGS. 30 and 31 are sectional views of a liquid crystal displayaccording to a third preferred embodiment of the present invention,which is an embodiment of changing the first embodiment of the presentinvention.

[0171] In this preferred embodiment, other components and structures ofthe top and the bottom substrates are the same as those related to thefirst preferred embodiment except that a common electrode 112 formed atthe top substrate has a different structure. That is, the entire surfaceof the common electrode 112 bears a surface roughness being mediumbetween the surface roughness of the first pixel electrode region 82 aand the surface roughness of the second pixel electrode region 82 b.

[0172] In this case, the liquid crystal molecules 151 interposed betweenthe first pixel electrode region 82 a bearing a small pretilt angle andthe common electrode 112 bearing a medium pretilt angle are twisted inthe first direction 1 pursuant to the pretilt angle of the commonelectrode 112 to thereby form a first liquid crystal domain, whereas theliquid crystal molecules 152 interposed between the second pixelelectrode region 82 b bearing a large pretilt angle and the commonelectrode 112 bearing a medium pretilt angle are twisted in the seconddirection 2 pursuant to the pretilt angle the common electrode 112 tothereby form a second liquid crystal domain. Therefore, two liquidcrystal domains that are twisted in different directions are present inone pixel region.

[0173] In order to make the surface roughness of the common electrode112 to be medium between the surface roughness of the first pixelelectrode region 82 a and the surface roughness of the second, pixelelectrode region 82 b, a layer for the common electrode 112 is depositedover the substrate, and its surface is treated. Such a surface treatmentis performed in the same way as with the pixel electrode 82 related tothe first preferred embodiment.

[0174] That is, inert gas may be bombarded on the surface of the targetlayer to partially remove the, surface, thereof in a physical manner.Alternatively, the top substrate may be dipped into an etching solutionfor a predetermined period of time to chemically etch the commonelectrode layer. The concentration of injection gas as well as the gasinjection energy, or the period of time for the dipping should beappropriately controlled to obtain the desired surface roughness.

[0175] A technique of controlling the strength of rubbing may be furtheremployed for making the liquid crystal molecules at the top substratebear the medium pretilt angle. An alignment layer (not shown) is formedon the common electrode 112, and is rubbed. At this time, the rubbingstrength is controlled such that grooves with a predetermined depth areformed at the alignment layer. In this way, the liquid crystal moleculesat the top substrate can bear a pretilt angle that is in the middlebetween the large pretilt angle and the small pretilt angle related tothe liquid crystal molecules at the bottom substrate.

[0176] Accordingly, a separate mask is not required to make the liquidcrystal molecules at the common electrode 112 bear the median pretiltangle.

[0177]FIG. 32 is a sectional view of a liquid crystal display accordingto a fourth preferred embodiment of the present invention.

[0178] In this preferred embodiment, other components and structures ofthe top substrate and the bottom substrate are the same as thoserelated, to the second preferred embodiment except that a commonelectrode 112 formed at the top substrate has a different structure.That is, the entire surface of the common electrode 112 has a surfaceroughness that is medium between the surface roughness of the firstpixel electrode region 82 a and the surface roughness of the secondpixel electrode region 82 b.

[0179] In this case, the liquid crystal molecules 151 interposed betweenthe first pixel electrode region 82 a bearing a small pretilt angle andthe common electrode 112 bearing a median pretilt angle are twisted inthe first direction 1 pursuant to the pretilt angle of the commonelectrode 112 to thereby form a first liquid crystal domain, whereas theliquid crystal molecules 152 interposed between the second pixelelectrode region 82 a bearing a large pretilt angle and the commonelectrode 112 bearing a median pretilt angle are twisted in the seconddirection 2 pursuant to the pretilt angle of the common electrode 112 tothereby form a second liquid crystal domain. Therefore, two liquidcrystal domains that are twisted in different directions are present atone pixel area.

[0180] In order to make the surface roughness of the common electrode112 to be medium between the surface roughness of the first pixelelectrode region 82 a and the surface roughness of the second pixelelectrode region 82 b, a layer for the common electrode 112 is depositedon the substrate, and the surface is treated. Such a surface treatmentis made in the same way as related to the third preferred embodiment.

[0181] As described above, in the inventive liquid crystal display, amulti domain structure where plural numbers of liquid crystal domainsare present in one pixel region is introduced to improve wide viewingangle characteristic. Furthermore, such a multi domain structure can berealized without using an additional mask.

[0182] While the present invention has been described in detail withreference to the preferred embodiments, those skilled in the art willappreciate that various modifications and substitutions can be madethereby without departing from the spirit and scope of the presentinvention as set forth in the appended claims.

What is claimed is:
 1. A method for fabricating a liquid crystaldisplay, comprising the steps of: forming a pixel electrode on a bottomsubstrate at each pixel area using a first mask such that the pixelelectrode has a first region with a smooth surface, and a second regionwith a rough surface, the bottom substrate having a gate wire, a datawire and thin film transistors: forming a common electrode on a topsubstrate using a second mask such that the common electrode has a firstregion with a smooth surface, and a second region with a rough surface,the top substrate having color filters; assembling the bottom substrateand the top substrate together; and injecting liquid crystal between thebottom substrate and the top substrate.
 2. The method of claim 1,wherein the bottom substrate is formed through the steps of: forming agate wire on a first insulating substrate, the gate wire comprising gateline, and gate electrode; forming a gate insulating layer such that thegate insulating layer covers the gate wire; forming a semiconductorpattern and a data wire on the gate insulating layer, the data wirecomprising data line, source electrode connected to the data line whilebeing connected to the semiconductor pattern, and drain electrode facingthe source electrode while being connected to the semiconductor pattern;forming a protective layer such that the protective layer covers thedata wire; and forming a first contact hole such that the first contacthole exposing the drain electrode.
 3. The method of claim 1, wherein thefirst mask comprises a first region transmitting light with a firstlight transmissivity, and a second region transmitting the light with asecond light transmissivity lower than the first transmissivity, thefirst region and the second region together defining the shape of thepixel electrode.
 4. The method of claim 3, wherein the first region hasa slit or lattice pattern.
 5. The method of claim 3, wherein the firstregion has a semitransparent pattern, and the second region has anopaque pattern.
 6. The method of claim 3, wherein each of the firstregion and the second region consists of a plurality of sub-regions, andthe sub-regions of the first region and the second region arealternately arranged.
 7. The method of claim 3, wherein the pixelelectrode is formed through the steps of: depositing a transparentconductive layer over the bottom substrate; coating a photoresist filmon the transparent conductive layer; selectively exposing thephotoresist film to light using the mask; forming a photoresist patternon the conductive layer through developing the light-exposed photoresistfilm, the photoresist pattern having a first photoresist portion placedover the first region of the pixel electrode with a first thickness, anda second photoresist portion placed over the second region of the pixelelectrode with a second thickness larger than the first thickness;etching the transparent conductive layer using the photoresist patternas a mask to form a shape of the pixel electrode; removing the firstphotoresist portion while exposing the underlying transparent conductivelayer; forming the first region of the pixel electrode through treatingthe surface of the exposed portion of the transparent conductive layer;and removing the second photoresist portion while exposing the secondregion of the pixel electrode.
 8. The method of claim 7, wherein thesurface is treated through bombarding inert gas on the exposed portionof the transparent conductive layer.
 9. The method of claim 7, whereinthe surface is treated through wet-etching the exposed portion of thetransparent conductive layer.
 10. The method of claim 7, wherein thefirst portion and the second portion of the photoresist pattern areremoved through dry etching.
 11. The method of claim 2, wherein thesemiconductor pattern and the data wire are formed throughphotolithography using a photoresist pattern with portions of thickness.12. The method of claim 11, wherein the photoresist pattern has a firstphotoresist portion placed over the data wire with a first thickness,and a second photoresist portion placed over the source electrode andthe drain electrode with a second thickness smaller than the firstthickness.
 13. The method of claim 12, wherein the semiconductor patternand the data wire are formed through the steps of: depositing asemiconductor layer and a conductor layer on the gate insulating layer,and forming the photoresist pattern oh the conductive layer; etching theconductive layer using the photoresist pattern as a mask while partiallyexposing the semiconductor layer; completing a semiconductor pattern byremoving the exposed portion of the semiconductor layer and the secondportion of the photoresist pattern while partially exposing theconductive layer between the source and the drain electrode; forming adata wire by removing the exposed portion of the conductive layer; andremoving the first portion of the photoresist pattern.
 14. The method ofclaim 11, wherein the photoresist pattern is formed using a mask, themask comprising a first region with a predetermined lighttransmissivity, a second region with a light transmissivity lower thanthe light transmissivity of the first region, and a third region with alight transmissivity higher than the light transmissivity of the firstregion.
 15. The method of claim 2, wherein the step of forming the datawire is done after forming the semiconductor pattern on the gateinsulating layer.
 16. The method of claim 1, wherein the top substrateis formed through the steps of: forming color filters on a secondinsulating substrate; and forming a common electrode such that thecommon electrode covers the color filters.
 17. The method of claim 16,wherein the common electrode is formed through the steps of: depositinga transparent conductive layer over the top substrate such that thetransparent conductive layer covers the color filters; coating aphotoresist film on the transparent conductive layer; selectivelyexposing the photoresist film to light using the second mask; forming aphotoresist pattern on the transparent conductive layer throughdeveloping the light-exposed photoresist film the photoresist patternhaving a first portion placed over the first region of the commonelectrode with a first thickness, and a second portion placed over thesecond region of the common electrode with a second thickness largerthan the first thickness; etching the transparent conductive layer usingthe photoresist pattern as a mask; removing the first portion of thephotoresist pattern while exposing the underlying transparent conductivelayer; forming the first region of the common electrode through treatingthe surface of the exposed portion of the transparent conductive layer;and forming the second region of the common electrode through removingthe second portion of the photoresist pattern.
 18. The method of claim17, wherein the surface is treated through bombarding inert gas on theexposed portion of the transparent conductive layer.
 19. The method ofclaim 17, wherein the surface is treated through wet etching the exposedportion of the transparent conductive layer using a wet etchingsolution.
 20. The method of claim 17, wherein the first portion and thesecond portion of the photoresist pattern are removed through dryetching.
 21. A liquid crystal display, comprising: a bottom substratewith a first region where liquid crystal molecules bear a first pretiltangle, and a second region where liquid crystal molecules bear a secondpretilt angle larger than the first pretilt angle; a top substratecorresponding to the bottom substrate with liquid crystal moleculesbearing a third pretilt angle, the third pretilt angle being mediumbetween the first pretilt angle and the second pretilt angle; and aliquid crystal layer sandwiched between the bottom and the topsubstrates with liquid crystal molecules, the liquid crystal moleculesbeing twisted at the first region in a first direction while beingtwisted at the second region in a second direction.
 22. The liquidcrystal-display of claim 21, wherein the bottom substrate comprises agate wire, a data wire crossing over the gate wire while being insulatedfrom the gate wire, thin film transistor electrically connected to thegate wire and the data wire, and pixel electrode electrically connectedto the thin film transistor, the pixel electrode bearing a first surfaceroughness at the first region while bearing a second surface roughnessat the second region, the second surface roughness being higher than thefirst surface roughness.
 23. The liquid crystal display of claim 22,wherein the top substrate comprises a common electrode corresponding tothe pixel electrode with a third surface roughness, and the thirdsurface roughness is in the middle between the first surface roughnessand the second surface roughness.
 24. Thee liquid crystal display ofclaim 22, wherein the top substrate comprises an insulating substrate, acommon electrode formed on the insulating substrate, and an alignmentlayer coated on the common electrode, the alignment layer having groovessuch that the liquid crystal molecules bear a third pretilt angle.
 25. Amethod of fabricating a liquid crystal display, comprising the steps of:forming a bottom substrate such that the bottom substrate has a firstregion where liquid crystal molecules bear a first pretilt angle, and aseconds region where liquid crystal molecules bear a second pretiltangle smaller than the first pretilt angle; forming a top substrate suchthat the top substrate faces the bottom substrate with liquid crystalmolecules bearing a third pretilt angle, the third pretilt angle beingmedium between the first pretilt angle and the second pretilt angle; andforming a liquid crystal layer such that the liquid crystal layer issandwiched between the bottom substrate and the top substrate withliquid crystal molecules, the liquid crystal molecules being twisted atthe first region in a first direction while being twisted at the secondregion in a second direction.
 26. The method of Claim 25, wherein thebottom substrate is formed through the steps of: forming a gate wire, adata wire and a thin film transistor on a first insulating substratesuch that the data wire crosses over the gate wire while being insulatedfrom the gate wire, and the thin film transistors are electricallyconnected to the data wire; and forming a pixel electrode such that thepixel electrode are electrically connected to the thin film transistor,each pixel electrode bearing a first surface roughness at the firstregion while bearing a second surface roughness at the second region,the second surface roughness being higher than the first surfaceroughness.
 27. The method of claim 26, wherein the pixel electrode areformed through the steps of: depositing a transparent conductive layerover the first substrate; coating a photoresist film on the transparentconductive layer; selectively exposing the photoresist film to lightusing a mask; forming a photoresist pattern on the transparentconductive layer through developing the light-exposed photoresist film,the photoresist pattern having a first portion placed over the firstregion of the common electrode with a first thickness, and a secondportion placed over the second region of the common electrode with asecond thickness larger than the first thickness; etching thetransparent conductive layer using the photoresist pattern as a mask toform a shape of the pixel, electrode; removing the first portion of thephotoresist pattern while exposing the underlying transparent conductivelayer; forming the first region of the pixel electrode through treatingthe surface of the exposed portion of the transparent conductive layer;and forming the second region of the pixel electrode through removingthe second portion of the photoresist pattern.
 28. The method of claim27, wherein the surface is treated through bombarding inert gas on theexposed portion of the transparent conductive layer.
 29. The method ofclaim 28 wherein the surface is treated through; wet-etching the exposedportion of the transparent conductive layer using a wet etchingsolution.
 30. The method of claim 25, wherein the step of forming thetop substrate is made through forming a common electrode on a secondinsulating substrate such that the common electrode corresponding to thepixel electrode with a third surface roughness, the third surfaceroughness being medium between the first surface roughness and thesecond surface roughness.
 31. The method of claim 30, wherein the commonelectrode is formed through the steps of: depositing a transparentconductive layer over the second substrate; and treating surface of thetransparent conductive layer such that the transparent conductive layerbears the third surface roughness.
 32. The method of claim 31, whereinthe surface is treated through bombarding inert gas on the exposedportion of the transparent conductive layer.
 33. The method of claim 32,wherein the surface is treated through wet-etching the exposed portionof the transparent conductive layer.
 34. The method of claim 25, whereinthe top substrate is formed through the steps of: forming a commonelectrode over a second insulating substrate such that the commonelectrode corresponds the pixel electrode; coating an alignment layercovering the common electrode; and rubbing the alignment layer such thatthe liquid crystal molecules at the top substrate bear the third pretiltangle.